Brick has long been a popular facing material for residential and commercial buildings. It is strong, durable, non-combustible and weather-resistant and requires little maintenance. Commonly, brick wall facing is provided in the form of a veneer wall. In a veneer wall, by definition, the facing is securely attached to a back-up structure but is not united with it such as to act in concert with the back-up in bearing applied loads.
A widely used back-up wall for commercial buildings is one based on steel studs, a gypsum wallboard exterior sheathing and a rigid plastic foam insulation applied over the sheathing. The brick veneer facing wall is carried on structural steel shelf angles at each story and is secured to the back-up wall, with an air space of 1" to 3" between it and the back-up wall, by anchors (sometimes called wall ties) located at 16-inch spacing vertically and either 16" or 24" spacing horizontally. The anchors are critical elements of the system, for they must support the veneer wall by transfer of lateral loads from the veneer wall to the back-up wall. Failure of the anchors means failure of the wall.
One type of anchor is a simple metal band corrugated transversely and bent into an "L" shape. The end portion of one leg of the "L" is embedded in a horizontal mortar joint of the brick veneer wall, and the other leg is fastened to the steel stud by screws. Another type of anchor comprises a slotted bracket that is welded or fastened by screws to the stud and receives a wire anchor member in a manner that allows vertical adjustment and movement of the anchor relative to the bracket.
The use of screws to fasten the anchor to the studs has recently been questioned. The presence of moisture due to leakage and condensation is inevitable, and corrosion of the screw threads is likewise inevitable. Corrosion-resistant coatings on the screws are disturbed when the screws are driven. Working of the screws weakens their hold to the stud. While welding provides the requisite strength, it is costly and requires complicated notching of the sheet rock and insulation, to expose the brackets. (Often, screw-fastened brackets are fastened on the face of the sheathing, which makes installation easier but also undesirably loads the sheathing and the screws.)
In Technical Notes on Brick Construction, No. 28B, Revised II, Feb. 1987, of the Brick Institute of America, Reston, Va., two designs for anchors are proposed in which one anchor element, either a wire or a plate, is fitted to the stud flange and a second element is attached to the first for vertical adjustment and movement and is embedded in the mortar joint. While those designs should provide longlife, as compared to screws, they are cumbersome in use, in that the first element has to be assembled to the stud before the stud is assembled to the back-up wall. In other words all of the anchor elements, which will usually be six or more, that are fitted to the stud have to be placed on the stud before the stud is erected. The chance of errors and omissions is great.